functions, optional parameters

[Mel Wilson]

On Sat, 09 May 2015 03:49:36 +1000, Chris Angelico wrote:

> Yes, but can you *distinguish* them in terms of default argument versus
> code object creation? How do you know that the function's code object
> was created when compile() happened, rather than being created when the
> function was defined? Is there anything that lets you in any way show
> different behaviour based on that timing difference?

This might show that default objects are fixed at run time:

Python 2.7.3 (default, Mar 14 2014, 11:57:14) 
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> a = []
>>> def b (arr=a):
...   arr.append ('c')
... 
>>> print repr(a)
[]
>>> b()
>>> print repr(a)
['c']
>>> b()
>>> print repr(a)
['c', 'c']
>>>